Process for the conversion of hydrocarbons to lighter hydrocarbons



A118128, 1934- G. F. FoRwooD v 1,972,013

PROCESS FOR TI-IE CONVERSION 0F HYDROCARBONS TO LIGHTER HYDROCARBONS Filed' Dec. 15, 1931 AITORNEY Patented ug. 28,1934

UNITED STATES PATENT OFFICE PROCESS FOR THE CONVERSION F HY- DROCARBONS TO LIGHTER HYDROCAR- BoNs George Frederick Forwood, West Chart, England 2 Claims.

This invention relates to a process for the conversion of hydrocarbons into lghterhydrocarbons, and has for its chief object the production of a material which will react in the pres- 5 ence of steam or water vapour for the production inter alia of nascent hydrogen, and which is more particularly applicable to processes which combine the principle of hydrogenation with that of molecular change or cracking in the hydrocarbon under treatment.

It is a well recognized fact that nascent hydrogen, in comparison with the non-nascent gas, is supremely active to achieve what is termed hydrogenation, and this effect must be accompanied by heat and frequently considerable pressure, and it is further known that iron in the form of wrought or cast iron shavings or small pieces is active under considerable heat to dissociate water when presented as steam. Iron however, is not in any sense a catalyst in that water on decomposition liberates hydrogen, but its oxygen content'combhes with the iron to form iron oxides which in turn cease to react further, and the iron oxide must be reduced to.

the metallic state as an intermediate operation before it can be reused for the process.

According to my invention a hydrocarbon may be converted into lighter hydrocarbons by heating a mixture of such hydrocarbon and steam to a high temperature in the presence of an alloy of iron which, when heated, will permit the decomposition of vwater without change so as to assist the cracking of the hydrocarbon and cause hydrogenation with the additional formation, probablyl of CO and/or CO2, and in which hydrogenation process it is not necessary -to apply any pressure other than that small pressure necessary for control of the hot vapours arising from the reaction vessel, say a few lbs. pressure per square inch.

The alloy of iron which I employ may consist of two parts by weight of tin and three parts by weight of iron of which the carbon contentis preferably low and from which adventitious impurities have been removed as far as possible.

In order to preserve the catalyst from chemical degradation and also to enhance the catalytic action thereof however, I prefer to employ an alloy of tin and iron to which a proportion of nickel is added, as I have found that the addition of nickel renders the catalytic action more lasting.

In carrying the invention into effect a catalyst may be made by melting in any convenient manner two parts by weight of tin (block quality),

three parts by weight of iron (wrought iron steel lor white cast iron filings or borings), in which feet, into a water vessel in which the water has "a temperature just under boiling point, say upwards of 180 deg. F. This causes the molten alloy to break up into nodular particles which remain brightish, and which are then ready for use in the reaction vessel. Whilst two parts of tin to three of iron are given as the preferred proportions a slightly less amount of tin may be used with certain qualities of irongwithout causing the iron to oxidize and it has been further found that for increasing the rate of reaction a small proportion of molybdenum say one per cent, may be added to the mix whilst hot and prior to drop quenching in water.

It has been found however, that whilst the catalyst made as described above will operate for a period of several runs in a cracking plant there is a tendency for the hydrogen gas produced to slow down, and the catalyst becomes inactive, and both microscopic and analytic investigation prove that this inactivity arises from oxidic degeneration of the iron in the alloy. Again, if the same catalyst be further employed, the nodules tend to disintegrate and compact, restricting the flow of oil vapour and causing carbonaceous deposits in the cracking zone. I have found however, that the catalyst can be preserved from chemical degradation and also rendered more active by the addition of nickel and the preferred catalyst embodying the present invention therefore comprises an alloy of tin and iron to which a proportion of nickel is added.

In preparing this preferred catalyst, iron in the form of commerciallypure filings or kindred type of comminution is admixed withv pure block tin and nickel in the proportion of:-

Two parts of tin by weight, one part of iron by weight, one part of nickel by weight; and whilst these proportions may be varied within'reasonable limits, the above represents a fair average of the most successful proportions.

If variation be required, it will be mainly necessitated by two reasons:-

(a) the necessity of working at a high temperature, i. e. 600 C. to 800 C.

(b) or due to the character of the iron.

Thus for (a) high temperatures, the tin may be 110 warrant granulation and prevent welding of the4 particles when the vessel base is reached.

Alternatively to nickel chromium or cobalt may be employed in approximately the proportion by weight as indicated above applying to nickel,

ferrochrome or cobalt iron being employed for the purpose, or again two or more of the substances, nickel, chromium and cobalt may be used in conjunction, the total proportion of these elements together in the alloy amounting to approximately 25%.

An apparatus suitable for carrying out the process is shown in the accompanying drawing, in which a represents a crackingcoil located in a furnace b of any suitable type. 'Ihe hydrocarbon is admitted to the coil a from a storage vessel c through apipe 1 controlled by a valve 2 and ows soA through the coil a into an evaporator d. Steam is also admitted to the coil a through a pipe 3 controlled by a valve 4. The catalyst employed in accordance with the invention is contained in the coil a, so that the mixture of hydrocarbon and steam is in contact with the catalyst as it is raised to the cracking temperature of approximately 600 in its passage through the coil a. 'Ihe treated hydrocarbon escapes into the evaporator d, within which the heavy oils separate to be drawn oi through a valve-controlled pipe 5. The light oil or spirit vapor passes from the evaporator d to a bubble tower e of any well known type adapted to separate the distillate into different fractions. The heavier vapor condensate separated by the bubble tower e is collected in a tank f and may be utilized as the fuel for heating thefurnace b.

I claim:

1. A, process for the conversion of hydrocarbons into lighter hydrocarbons, comprising heating a mixture of hydrocarbon and steam to a temperature of approximately 600 C. in the presence of a catalyst consisting of two parts by weight of tin, one part by weight of iron, and one part by weight of one of the metals included in the group nickel, chromium and cobalt, under a pressure only suflicient to control the hot vapors arising in the vessel in which the reaction is produced.

2. A process for the conversion oi' hydrocarbons into lighter hydrocarbons, comprising heating a mixture of hydrocarbon and steam to a temperature of approximately 600 C. in the presence of a catalyst consisting of two parts by weight of tin, one part by weight of iron, and one part by weight of nickel, under a pressure only sufficient to control the hot vapors arising in the vessel in which the reaction is produced.

GEORGE. FREDERICK FORWOOD.

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